Accelerating Frames and Pseudo Force
For translational frame acceleration A, m a_rel=sum F_real-mA; this simple form excludes rotating-frame terms.
Why this shows up in the exam
Accelerating wedges · Vehicle pendulums · Rocket equilibrium
Learn the idea
In a translating non-inertial frame add -mA_frame to every mass. An accelerating wedge, car, or rocket creates an effective gravity tilted opposite frame acceleration.
🧠 Memory hook: Frame accelerates one way; pseudo force points the other.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- F_pseudo = -m A_frame — translational pseudo force
- g_eff = g_vector-A_frame — effective gravity
- m a_rel = sum F_real-m A_frame — frame equation
How to approach it
- 1State frame
- 2Draw -mA if needed
- 3Resolve real plus pseudo forces
Common slip-ups that cost marks
- •Pseudo force in inertial frame
- •Wrong sign
- •Ignoring rotational terms
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A 2 kg block moves on a horizontal rough surface with coefficient of kinetic friction 0.2. A horizontal force of 10 N acts on it. Take g = 10 m/s^2. What is its acceleration?
More from Laws of Motion
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In an inertial frame sum F_ext = dp/dt; for constant mass this becomes m dv/dt = ma.